The RĂ©pertoire International des Sources Musicales is a worldwide inventory of more than one million primary sources in music, including manuscripts, prints, libretti, and writings on music theory. It is used to discover what sources are available and where they are located; for some, links to digital images are also provided. This freely available catalog contains all of RISM Series A/I, Individual Prints before 1800, all of Series A/II, Music Manuscripts 1600-1800, and the portion of Series B/I, Printed Collections of the 16th-17th Centuries, that covers the years 1500-1550. This comprises about one-third of the manuscripts and more than half of the music prints that were produced before 1800 and that are held by libraries today. Works of approximately 30,000 composers are described.